1. Field of the Invention
The present invention relates to a multi-layered object having a hard coat layer, and a method for producing the multi-layered object. More specifically, the present invention relates to various multi-layered objects required to have anti-staining property, anti-staining durability, scratch resistance, abrasion resistance and the like, and having a hard coat layer which has these various properties on the surface thereof; and relates to a method for producing the multi-layered objects.
In particular, the present invention relates to a method for forming a hard coat layer having anti-staining property, anti-staining durability, scratch resistance, and abrasion resistance, on the surface of each of the following, without deteriorating the optical property and the recording properties: information recording media; optical lenses; optical filters; anti-reflective films; various display elements such as liquid crystal displays, CRT displays, plasma displays and EL displays; and the like, and relates to an article having the hard coat layer formed thereon.
2. Disclosure of the Related Art
Usually protective layers (hard coat layers) are provided on the surfaces of the following various articles required to have scratch resistance and abrasion resistance: information recording media such as CD (Compact Disc) and DVD (Digital Versatile Disc); optical lenses; optical filters; anti-reflective films; and various display elements such as liquid crystal displays, CRT displays, plasma displays and EL displays.
In these various articles, in the course of the use by users, the surface thereof frequently undergoes stain adhesion due to fingerprint, sebum, sweat and cosmetics. Once adhesion of such stains occurs, such stains can hardly be removed; in particular, in information recording media and optical lenses used for the recording and reproduction thereof, such stains result in significant failure in recording and reproduction of information signals to cause a serious problem.
In particular, information recording media such as BD (Blu-ray Disc) said to be next-generation DVD are undergoing adoption of shorter wavelength of recording/reproduction laser light, and high-density recording with objective lenses having high numerical apertures; along with such development, the light transmitting substrate (light transmitting layer) comes to be thinner and accordingly there occurs a possibility that minute scratches, stains and the like on the light incident-side surface cause crucial failure in recording/reproduction in a more severe manner than in conventional information recording media. From these reasons, it is strongly demanded to provide, on the light incident-side surface of the information recording media, a hard coat layer having anti-staining property, anti-staining durability, scratch resistance and abrasion resistance, without deteriorating the recording/reproduction properties.
As a method of improving the anti-staining property of a hard coat layer, there has been proposed a method of improving the anti-staining property (water repellency and oil repellency) of the surface of an information recording medium by applying silicone oil or a fluoropolymer to the surface of the hard coat layer. However, in this method, the hard coat layer is formed by applying an anti-staining agent onto the surface of the information recording medium, and hence this method offers a drawback that the anti-staining agent is dissipated in the course of the use by a user and consequently the effect of the anti-staining property is hardly maintained, that is, the hard coat layer is poor in anti-staining durability.
On the other hand, there is a method of improving the anti-staining property by incorporating an additive such as silicone oil or a fluoropolymer into the hard coat layer. However, these additives are the substances generally referred to as soft segment and have a property to impart flexibility to a resin, and hence the addition of these additives offers a drawback to degrade the mechanical strength of the hard coat layer such as the surface hardness as a function of the hard coat layer.
For example, Japanese Patent Laid-Open No. 2004-047040 (Patent Document 1) describes an optical recording medium characterized in that a coating layer made of an anti-staining agent is formed on the reading side surface on which incident is the laser light conducting at least recording or reproduction of the information signal (claim 1). However, the anti-staining agent described in Patent Document 1 includes an alkoxysilane compound having a perfluoro polyether group or a fluoroalkyl group, and is different from the composition for the hard coat layer according to the present invention.
Japanese Patent Laid-Open No. 2002-367229 (Patent Document 2) describes an optical information recording medium in which at least a reflective film, a recording film and a protective film are provided on one surface of the substrate of the optical information recording medium, and the protective film is formed as a surface layer on the one surface of the substrate, wherein a hard coat resin layer is formed as an outer layer of at least one selected from the substrate and the protective film, and a chemical adsorption film made of organic silane molecules is formed as an outer layer of the hard coat resin layer so as to be bonded to the hard coat layer through a covalent bond (claim 1). The hard coat layer of Patent Document 2 is, as described therein, a so-called double layered hard coat layer in which the chemical adsorption film formed by covalent bonds is further provided on the surface of the hard coat resin layer, and is significantly different in constitution from the hard coat layer of the present invention.
Japanese Patent Laid-Open No. 2006-107572 (Patent Document 3) describes a hard coat surface treatment method wherein a hard coat surface formed by curing an organic hard coat material containing an energy ray curable compound is subjected to a plasma treatment in an atmosphere into which introduced is a gas of a fluorinated hydrocarbon containing fluorine atoms in the molecule (claim 1). Patent Document 3 describes that according to this method, there is provided a hard coat surface treatment method in which the medium surface is imparted with water repellency and oil repellency by means of a low cost and simple process; however, this method requires a specific large scale apparatus in order to conduct the plasma treatment under a specific atmosphere, and hence is insufficient as a simple and low cost process.
Japanese Patent Laid-Open No. 2003-277478 (Patent Document 4) describes an epoxy resin composition that includes: an epoxy resin having in one molecule at least two cyclic aliphatic epoxy groups, at least one perfluoroalkyl group having 6 to 12 carbon atoms and at least one alkylsiloxane group; and a cationic polymerization catalyst, wherein the cyclic aliphatic epoxy group and the perfluoroalkyl group are present in the branched chains of the epoxy resin, and the alkylsiloxane group is present in the main chain of the epoxy resin (claim 1). Patent Document 4 is concerned with a composition that is applied to a liquid jet recording head, and the layer formed from the composition has anti-staining property, but is insufficient for a hard coat layer that also has the mechanical strength such as the surface hardness required in information recording media, various display elements or the like.
Japanese Patent Laid-Open No. 2005-206829 (Patent Document 5) describes a fluorine-containing curable coating liquid containing a fluorine-containing compound having a film formability and a polymerizable double bond, and a fluorine-containing (meth)acrylic acid ester having no film formability (claim 1). Similarly to Patent Document 4, the layer formed from the coating liquid of Patent Document 5 has anti-staining property, but is insufficient for a hard coat layer that also has the mechanical strength such as the surface hardness required in information recording media, various display elements or the like. As a technique to improve the surface hardness, it is possible to provide a hard coat layer and to form thereon a fluorine-containing curable coating film; however, this method suffers from a trouble that the fluorine-containing curable coating film is dissipated in the course of the use by a user to lead to poor anti-staining durability.
Japanese Patent Laid-Open No. 11-43648 (Patent Document 6) describes a curable resin composition for a coating material including: (a) a silicone-acrylic block copolymer obtained by polymerizing at least one kind of acrylic monomer having a cross-linkable functional group or a mixture composed of said acrylic monomer and another ethylenically unsaturated monomer in the presence of a silicone macro initiator that includes a plurality of polysiloxane chains having both terminals linked with a 2,2′-azobisnitrile group; (b) a film forming resin having a functional group capable of cross-linking with the same curing agent as for the cross-linkable functional group of the (a) component, or having a functional group that mutually reacts with the functional group of the (a) component; and (c) a curing agent that reacts at least with the (b) component (claim 1). However, the composition described in Patent Document 6 is different from the composition applied to the present invention, and is insufficient for the hard coat layer having anti-staining property, anti-staining durability, scratch resistance and abrasion resistance, without impairing the optical properties and the recording properties as required for information recording media and various display elements.
Japanese Patent Laid-Open No. 2002-363495 (Patent Document 7) describes a coating composition including: (a) a fluorine/silicone-acrylic block copolymer obtained by polymerizing a monomer mixture A including a fluorine-containing unsaturated monomer (a-1) and an acrylic monomer (a-2) having a reactive functional group, in the presence of a silicone macro initiator that includes a plurality of polysiloxane chains having both terminals linked with a 2,2′-azobisnitrile group; (b) a fluorine-containing copolymer obtained by polymerizing a monomer mixture B including a fluorine-containing unsaturated monomer (b-1) and an acrylic monomer (b-2) having a reactive functional group; and (c) a curing agent (claim 1). However, the composition described in Patent Document 7 is different from the composition applied to the present invention, and is insufficient for the hard coat layer having anti-staining property, anti-staining durability, scratch resistance and abrasion resistance, without impairing the optical properties and the recording properties as required for information recording media and various display elements.